MEASUREMENT OF RESIDUAL STRAIN IN INGAAS BUFFER LAYERS

InxGa1-xAs layers have been grown with different indium compositions a nd thicknesses above the critical layer thickness and the extent of st rain relaxation has been measured using high-resolution x-ray diffract ion. Our results show that, in thick layers, the residual strain is de pendent upon the lattice mismatch. In a range from 30 times up to 300 times the critical layer thickness, the residual strain represents abo ut 15% of the lattice mismatch, regardless of the In composition. Comp arison with published experimental data shows that the magnitude of th e residual strain is difficult to predict and depends upon parameters which are yet to be identified. Our data also shows a different behavi or for a sample with thickness 450 times the critical layer thickness where strain relaxation is almost complete. One possible explanation i s a relaxation process which takes place during the growth of the stru cture, leading to a time dependent lattice mismatch.